Generally, wireless communications systems using beamforming utilize a number of transmit and/or receive antennas and signal processing to create fixed or adaptive transmit and/or receive beam patterns. The beam patterns may have a directional nature that results in a performance improvement when compared with unidirectional transmit and/or receive antennas. The use of beam patterns may yield a transmit/receive gain over wireless communications systems using unidirectional transmit and/or receive antennas. Beamforming therefore may help increase cell coverage and improve cell edge spectral efficiencies.
According to an existing beamforming solution, a fixed downward tilting angle is generally provided in the vertical direction, i.e., providing a fixed beam in the vertical direction for each user equipment (UE) in a cell. Such a solution fixes a beamforming weight in the vertical direction, leading to a finer and narrower beam in the vertical direction, thus it may reduce the interference with neighboring cells and enhance system throughput to a certain extend.
However, although the solution of fixed down tilting angle may improve cell throughput to a certain extent, a major lobe of the radiation pattern of an antenna may only be directed to a UE in a certain direction within the cell, but for other UE(s) deviating from the certain direction, the receiving power(s) will be significantly decreased. Further, the solution with a fixed beam in the vertical direction may have negative effect on beam scheduling and interference coordination between neighboring cells in the vertical direction.
In view of the foregoing problem, there is a need to find a solution of three-dimensional (3D) beamforming to adjust the vertical direction of a beam while adjusting the horizontal direction of the beam, so as that the beam effectively tracks a UE in both the vertical direction and the horizontal direction.